Segmented heat sink for natural-convection cooled systems

ABSTRACT

Various exemplary embodiments relate to a heat sink system. The heat sink system may include: a first heat sink segment including a first fluid inlet and a first fluid outlet having an outlet flow path; and a second heat sink segment including a second fluid inlet having an inlet flow path and a second fluid outlet. The second heat sink segment may be arranged in a placement position within the heat sink system so that the second fluid inlet receives fluid from substantially other sources than the first outlet flow path. Various exemplary embodiments relate to a heat sink segment. The heat sink segment may include: a base plate; a plurality of vertical fins; a horizontal wall; a first fluid opening; and a second fluid opening. The first fluid opening may face a different direction than the second fluid opening.

TECHNICAL FIELD

Various exemplary embodiments disclosed herein relate generally to heat sinks for dissipating heat from a heat source.

BACKGROUND

Many types of electronic components require cooling in order to maintain a suitable working temperature. A heat sink is used to draw heat away from an electronic component and dissipate the heat, usually into a fluid. A heat sink increases the surface area in contact with a surrounding cooling fluid such as air.

SUMMARY

A brief summary of various exemplary embodiments is presented. Some simplifications and omissions may be made in the following summary, which is intended to highlight and introduce some aspects of the various exemplary embodiments, but not to limit the scope of the invention. Detailed descriptions of a preferred exemplary embodiment adequate to allow those of ordinary skill in the art to make and use the inventive concepts will follow in later sections.

Various exemplary embodiments relate to a heat sink system. The heat sink system may include: a first heat sink segment, the first heat sink segment including a first fluid inlet and a first fluid outlet having an outlet flow path, the first heat sink segment being positioned in a first placement position within the heat sink system; and a second heat sink segment, the second heat sink segment including a second fluid inlet having an inlet flow path and a second fluid outlet, the second heat sink segment being positioned in a second placement position within the heat sink system based on the first placement position. The second placement position may be arranged so that the second fluid inlet receives fluid from substantially other sources than the first outlet flow path.

In various alternative embodiments, the second placement position is arranged vertically above and adjacent to the first placement position.

In various alternative embodiments, the second fluid inlet is located on a different face than the first fluid outlet. The outlet flow path may be approximately perpendicular to the inlet flow path.

In various alternative embodiments, the heat sink system further includes a cover plate including a first opening that at least partially defines the first fluid inlet and a second opening that at least partially defines the first fluid outlet. The cover plate may include a vertical baffle located between the first fluid outlet and the second fluid inlet.

In various alternative embodiments, the first fluid outlet includes a plurality of pins projecting outwardly from the heat sink. In various alternative embodiments, the second fluid inlet includes a plurality of pins projecting outwardly from the heat sink.

In various alternative embodiments, the heat sink system may further include a horizontal wall separating the first heat sink segment and the second heat sink segment.

In various alternative embodiments, the first placement position overlaps the second placement position and at least one of the first heat sink segment and the second heat sink segment is oriented at an angle. The first fluid outlet may be above the second fluid inlet. One of the first fluid inlet and the first fluid outlet may be located at an end face of the first heat sink segment.

Various exemplary embodiments relate to a heat sink. The heat sink may include: a base plate; a first heat sink segment comprising: a first plurality of vertical fins extending outwardly from the base plate toward a front face, a first fluid inlet, and a first fluid outlet; a second heat sink segment comprising: a second plurality of vertical fins extending outwardly from the base plate toward a front face, a second fluid inlet, and a second fluid outlet, the second heat sink segment located vertically above the first placement position; and a cover at least partially enclosing the first plurality of vertical fins and the second plurality of vertical fins and defining the first fluid outlet and the second fluid inlet.

In various alternative embodiments, one of the first fluid outlet and the second fluid inlet is located on a front face of the heat sink system, and the other of the first fluid outlet and the second fluid inlet is located on a side face of the heat sink system.

In various alternative embodiments, the heat sink further includes a plurality of pins extending outwardly from the base plate toward the front face.

In various alternative embodiments, the heat sink further includes a horizontal wall separating the first heat sink segment and the second heat sink segment.

In various alternative embodiments, the heat sink further includes a duct adjacent one of the first fluid outlet and the second fluid inlet.

Various exemplary embodiments relate to a heat sink segment. The heat sink segment may include: a base plate; a plurality of vertical fins, each fin extending outward from the base plate toward a front face; a horizontal wall extending outward from the base plate at a first end of the plurality of vertical fins; a first fluid opening located at the first end of the heat sink segment; and a second fluid opening located at a second end of the heat sink segment. The first fluid opening may face a different direction than the second fluid opening.

In various alternative embodiments, the heat sink segment further includes a cover panel at least partially enclosing the plurality of vertical fins and defining the first fluid opening and the second fluid opening. The heat sink segment may also include a plurality of spaced apart pins extending from the base plate toward the cover panel, wherein the cover panel defines openings on two side faces of the heat sink segment. One of the first fluid opening and the second fluid opening may be a gap in the cover that exposes a portion of the vertical fins along the edges of the fins.

In various alternative embodiments, the heat sink segment further includes a plurality of curved fins extending from the base plate toward the cover panel, the curved fins extending from one of the first fluid opening and the second fluid opening toward the plurality of vertical fins.

In various alternative embodiments, the first fluid opening is located on the front face of the heat sink segment and the second fluid opening is located on a face opposite the front face.

In various alternative embodiments, the heat sink segment further comprises a duct or plenum.

It should be apparent that, in this manner, various exemplary embodiments enable a segmented heat sink. In particular, by isolating an outlet air flow from an inlet air flow, the segmented heat sink may reduce reentrance of heated air.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand various exemplary embodiments, reference is made to the accompanying drawings, wherein:

FIG. 1A illustrates a perspective view of an electronics unit with an exemplary segmented heat sink;

FIG. 1B illustrates a side view of the electronics unit and exemplary segmented heat sink of FIG. 1A;

FIG. 1C illustrates a cross sectional view of FIG. 1A along the line C;

FIG. 2 illustrates a side view of another embodiment of a segmented heat sink;

FIG. 3 illustrates a side view another embodiment of a segmented heat sink;

FIG. 4 illustrates another embodiment of a segmented heat sink;

FIG. 5 illustrates another embodiment of a heat sink segment; and

FIG. 6 illustrates another embodiment of a heat sink segment.

DETAILED DESCRIPTION

Cooling systems for outdoor electronics components located on top of a mast or tower may face several challenges. The location may limit the size and weight of a heat sink. Moving parts such as fans and motors may wear out leading to an expensive and dangerous procedure to replace the part. Accordingly, an outdoor application may use an air-cooled natural convection heat sink. Such a heat sink may include a plurality of vertically oriented fins that dissipate heat. It should be appreciated that air-cooled natural convection heat sinks are not limited to cooling systems for outdoor electronic components.

Some electronic's applications use vertically arranged arrays of electronic components. Such arrays may include a heat sink with vertically oriented fins. In such a heat sink, the fins heat the surrounding air, causing it to rise in a natural convection current. One problem faced by such heat sinks is that as air is heated and moves upward, the fins are able to dissipate less heat into the preheated air while maintaining the electronic components at or below a desired temperature. Accordingly, electronics components located at the top of an array may receive less cooling than components located lower in the array. In order to achieve sufficient cooling, the entire heat sink may be made larger, increasing cost and weight.

A segmented heat sink may be used to prevent the increase in temperature of a cooling medium such as air toward the top of a heat sink. When a heat sink is divided into a plurality of segments, cooler ambient air may be brought into each segment. Each segment may act as an individual heat sink and provide greater cooling. A segmented heat sink may not operate efficiently if the exhausted heated air of one segment reenters another segment as ambient air.

In view of the foregoing, it would be desirable to provide effective cooling for vertically arrayed electronics components in an outdoor application. In particular, it would be desirable to use a segmented heat sink utilizing natural convection cooling that minimizes reentrance of heated air into the heat sink.

Referring now to the drawings, in which like numerals refer to like components or steps, there are disclosed broad aspects of various exemplary embodiments.

FIG. 1A illustrates a perspective view of an electronics unit with an exemplary heat sink 100. Reference will also be made to FIG. 1B, which illustrates a side view of the electronics unit and heat sink 100, and FIG. 1C, which illustrates a cross sectional view of heat sink. 100 along line C. Heat sink 100 may include a plurality of heat sink segments 120 a-n. Heat sink segments 120 a-n may be mounted on a heat source 50, or on multiple distributed heat sources. Although two heat sink segments are shown in FIG. 1A, any number n of heat sink segments 120 a-n may be mounted to a heat source 50. The exact size and shape of heat sink 100 and heat source 50 may vary depending on the use of the electronics unit.

Heat source 50 may include any electronics component or other component that produces heat for which cooling is desirable. Heat source 50 may include, for example, an active antenna array, radio-on-chip, power amplifier, and other heat producing components. In various exemplary embodiments, heat source 50 may include multiple modular components. The components may be interconnected or distributed elements that are not physically connected. The components may be arrayed vertically. The components may produce varying amounts of heat, or the heat may be distributed evenly.

Heat sink segments 120 a-n may form a heat sink 100 for dissipating the heat produced by heat source 50. FIG. 1A illustrates a heat sink with two heat sink segments 120 a and 120 n. Additional heat sink segments 120 may be added above heat sink segment 120 n or below heat sink segment 120 a. Heat sink segments 120 may be made in varying heights to meet cooling and space requirements. Heat sink segments 120 a-n may be made from a material with high thermal conductivity such as, for example, aluminum alloy, magnesium alloy, copper alloy, or other materials known by those skilled in the art. Heat sink segments 120 a-n may be placed adjacent heat source 50. In various embodiments, thermal adhesive or thermal grease may be used to improve the thermal performance between the heat source 50 and heat sink segments 120 a-n. In some instances, the base 130 n may be integral with the enclosure or package containing the heat source. Heat sink segments 120 a-n may be positioned to correspond to locations of electronics components of heat source 50. In various embodiments, the heat sink segments 120 a-n may be adjacent each other.

Each heat sink segment 120 a-n may include: base 130, cover 140, inlet 150, lower wall 155, pins 160, vertical fins 165, outlet 170, and upper wall 175.

Base 130 may be a flat plate of material adjacent to heat source 50. Base 130 may extend horizontally and vertically across the entire face of heat source 50. In various embodiments, multiple heat sink segments 120 a-n may be formed on the same base 130. Alternatively, a heat sink segment 120 may have an individual base 130.

Cover 140 may be a piece of material that covers heat sink segment 120. Cover 140 may be made from a material with a higher thermal resistance, i.e., a lower thermal conductivity, such as, for example, plastic. Cover 140 may include openings defining inlet 150 and outlet 170 of a heat sink segment 120. Cover 140 may also include horizontal lower wall 155 and horizontal upper wall 175. As shown in FIGS. 1 a and 1B, cover 140 may include a front face 142 a and a side face 144 a. In various embodiments, cover 140 may include only front face 142 a, and a vertical fin 165 may form the side face of heat sink segment 120. Cover 140 may at least partially define opening 150 by providing a gap in side face 144.a. Cover 140 may define opening 170 by providing a gap in front face 142 a. Cover 140 may, in conjunction with base 130 and vertical fins 165 may define an opening 150 and/or an opening 170. Cover 140 may act as a solar shield to reduce the absorption of solar radiation by the heat sink segment 120. Cover 140 may also act as a protective shield to prevent damage to heat sink segment 120. Cover 140 may also act to direct the airflow through heat sink segment 120. The opening for inlet 150 may allow ambient air to flow to the interior of heat sink segment 120. The opening for outlet 170 may allow heated air to flow out of heat sink segment 120.

Inlet 150 may be an opening in heat sink segment 120 and cover 140 that allows ambient air to enter the interior of heat sink segment 120. Inlet 150 may be located near the bottom end of heat sink segment 120 to allow ambient air to enter near the bottom. As the air is heated inside the heat sink segment 120, buoyancy may cause the heated air to rise, and more ambient air may be drawn in through inlet 150. In various exemplary embodiments, as shown in FIG. 1A, inlet 150 may include an opening on each side of heat sink segment 120. As shown, such openings may face the lateral sides of heat sink segment 120 and draw ambient air from the lateral sides. An inlet flow path may be directed from one or more lateral sides toward the interior of the heat sink segment 120. A path may be the direction along which the fluid is primarily flowing at a particular location within the heat sink. To be more specific, the path may correspond to the velocity vector associated with the fluid motion at a particular location. For example, between a set of long, vertically-oriented fins that are in contact with a heat sink base that is in contact with a heat source, the path may be primarily in the vertical direction. i.e., the velocity vector associated with the fluid motion may be primarily vertical as buoyancy forces are causing the fluid to rise vertically. As will be described in further detail below, other embodiments may have one or more inlets located in different positions at the bottom end of heat sink segment 120.

Pins 160 may form a portion of heat sink segment 120. Pins 160 may be a plurality of pin fins. Pins 160 may extend from base 130 outward toward cover 140. Pins 160 may be integrally formed with base 130 by processes such as, for example, extrusion, die casting, skiving, press fitting or machining. Alternatively, pins 160 may be soldered or welded to base 130. Pins 160 may be arranged in any pattern on base 130. Pins 160 may include any arrangement of fins that allows air flow in two directions, e.g., horizontally and vertically. The pins 160 may be square, round, triangular, diamond-shaped, rectangular, or some other shape. The pins 160 may be arranged in an array like fashion, such as a grid that has regular spacing, like a lattice or in a less regular structure.

Pins 160 may dissipate heat from base 130 into the surrounding air, while allowing air to flow in different directions around pins 160. For example, in the embodiment shown in FIG. 1A, ambient air entering heat sink segment 120 from inlet 150 may flow horizontally from the lateral sides of heat sink segment 120 toward the center. The entering air may also flow vertically upward as it is heated. In various alternative embodiments, pins 160 may be replaced with curved fins. The curved fins may extend from an opening toward vertical fins 165. Curved fins may allow air to flow in the desired direction while also providing heat dissipation. Other types of fins, such as angled straight fins, may also be used to allow air flow in the desired direction while also providing heat dissipation. In various alternative embodiments, pins 160 may be absent, leaving a finless portion. A finless portion may allow optimal airflow but less surface area.

Vertical fins 165 may form a portion of heat sink segment 120. Vertical fins 165 may be a plurality of parallel vertical fins. Vertical fins 165 may extend outward from base 130 toward cover 140. Vertical fins 165 may be integrally formed in base 130 by processes such as, for example, machining, extrusion, die casting, press fitting and skiving. Alternatively, vertical fins 165 may be soldered or welded to base 130. Vertical fins 165 may dissipate heat from base 130. As shown in FIG. 1C, vertical fins 165 may be wider near base 130 than at the top edge. In various exemplary embodiments, vertical fins 165 may be spaced approximately 1 cm apart. In various embodiments, vertical fins 165 may be spaced anywhere from 5 mm to 15 mm apart. Vertical fins 165 may use natural convection cooling based on the buoyancy of heated air. As the air between vertical fins 165 is heated, it may rise upward toward the top of heat sink segment 120. In various exemplary embodiments, as shown in FIG. 1A, a portion of vertical fins 165 may be located beneath cover 140. Another portion of vertical fins 165 may be exposed by an opening in cover 140. In various exemplary embodiments, vertical fins 165 may extend vertically to a horizontal wall of the heat sink segment. In various embodiments, vertical fins 165 may not extend to a horizontal wall of the heat sink segment, forming a gap that may at least partially define an inlet or outlet.

Outlet 170 may be an opening in heat sink segment 120 and cover 140 that allows heated air to exit the heat sink segment 120. Outlet 170 may be located near the top of heat sink segment 120. In various exemplary embodiments, as shown in FIG. 1A, outlet 170 may be formed by an opening in cover 140 along the front face of heat sink segment 120. Outlet 170 may exhaust heated air out the front face of heat sink segment 120. An outlet flow path may be directed from the interior of heat sink segment 120 toward the forward face of heat sink segment 120. It may be noted, that outlet 170 may face a different direction than inlet 150. For example, outlet 170 may face the front of the heat sink segment, whereas inlet 150 may face the lateral sides of the heat sink segment. In various embodiments, inlet 150 and outlet 170 may be located on approximately orthogonal faces of heat sink segment 120. The approximately orthogonal faces may be oriented between 80 degrees and 100 degrees of each other.

Lower wall 155 may be a horizontal barrier that prevents fluid from entering via the bottom face of heat sink segment 120. Lower wall 155 may be present when heat sink segment 120 is located adjacent another heat sink segment. In particular, lower wall 155 may divide an upper heat sink segment from a lower heat sink segment. If heat sink segment 120 is a bottom segment, lower wall 155 may be absent, allowing air to enter from the bottom surface of heat sink segment 120. Lower wall 155 may be made from a thermally resistant material, such as, for example, plastic. In various embodiments, lower wall 155 may be formed as part of cover 140.

Upper wall 175 may be a horizontal barrier that prevents fluid from exiting via the top edge of heat sink segment 120. Upper wall 175 may be present when heat sink segment 120 is located adjacent another heat sink segment. In particular, upper wall 175 may divide a lower heat sink segment from an upper heat sink segment. If heat sink segment 120 is the top segment, upper wall 175 may be absent, allowing air to exit from the top surface of heat sink segment 120. Upper wall 175 may be made from a thermally resistant material, such as, for example, plastic. In various embodiments, upper wall 175 may be formed as part of cover 140. In various embodiments, upper wall 175 of one heat sink segment may form the lower wall 155 of an adjacent heat sink segment. Alternatively, upper wall 175 and lower wall 155 may be separate adjacent walls.

A heat sink segment 120 may be oriented in the opposite direction, that is, upside down. In such an embodiment, outlet 170 may be located at the bottom of the heat sink segment 120 and act as an inlet. Inlet 150 may be located at the top of the heat sink segment 120 and act as an outlet. Likewise the orientation of upper wall 175 and lower wall 155 may be reversed.

Having described various structural components of a heat sink segment 120 and heat sink 100, a brief overview of the functionality of the heat sink 100 will be provided. It should be apparent that the structural components of heat sink 100 or similar components may be used to design heat sinks with similar functionality.

Base 130 may be in thermal contact with heat source 50. Heat from heat source 50 may spread across base 130 due to the thermal conductivity of the base material. Heat may also spread into pins 160 and vertical fins 165 from base 130. Heat may also radiate away from the base 130, pins 160, and vertical fins 165.

Cool ambient air may enter heat sink segment 120 a via inlet 150 a. In the first portion including pins 160 a, the air may receive heat from base 130 a and pins 160 a. The air may move upwards into the portion including vertical fins 165. Vertical fins 165 a and base 130 a may provide additional surface area for radiating heat. The air may continue to move upward toward outlet 170. In the portion near outlet 170, vertical fins 165 a may be exposed. The rising warm air may exit heat sink segment 120 a via outlet 170 a. Upper wall 175 a may prevent the warm air from entering heat sink segment 120 n. The warm air may continue to rise, primarily passing in front of cover 140 n. Heat sink segment 120 n may draw ambient air from the lateral faces of heat sink 100. Accordingly, heat sink segment 120 n may draw air from substantially other sources than the outlet 170 a. The substantially other sources may provide at least fifty percent of the air, by volume, entering heat sink segment 120 n.

FIG. 2 illustrates a side view of another embodiment of a segmented heat sink 200. Segmented heat sink 200 may include a plurality of heat sink segments 220 a adjacent a heat source 52. In various embodiments, heat source 52 may also be segmented into a plurality of heat sources 52 a-c. Segments of heat source 52 may correspond to electronic components. As shown in FIG. 2, each heat sink segment 220 may be positioned at an angle from a vertical line. An angle may allow individual heat sink segments 220 to be longer. Individual heat sink segments 220 may overlap. The angle may also allow beneficial positioning of inlets 250 and outlets 270. An angle may reduce the buoyant effect of warmed air and reduce air flow through a heat sink segment.

A middle heat sink segment 220 b may illustrate characteristics of this embodiment. Heat sink segment 220 b may include similar components to a heat sink segment 120 as discussed above. Base 230 b may be in thermal contact with heat source 52 b. In various embodiments, base 230 b may extend along a bottom end of heat sink segment 220 b and be in thermal contact with heat source 52 a. Cover 240 b may cover the entire front surface of heat sink segment 220 b. In particular, cover 240 b may separate inlet 250 b from outlet 270 a. Cover 240 b may include openings on the side faces of heat sink 200 for inlet 250 b. Alternatively, cover 240 b and openings in vertical fins (not shown) located along the edge of base 230 b may define the inlet 250 b. Inlet 250 b may be located substantially below outlet 270 a, such that at least fifty percent of inlet 250 b is below outlet 270 a, to prevent warm air from outlet 270 a from entering inlet 250 b. Pins 260 b may extend outward from base 230 b and dissipate heat in the portion near opening 250 b. Vertical fins (not shown) may be located inside cover 240 b. The vertical fins may extend from base 230 b and dissipate heat as air rises within heat sink segment 220 b. Outlet 270 b may be located at the top end face of heat sink segment 220 b. Outlet 270 b may exhaust warm air substantially vertically. Outlet 270 b may be positioned such that an outlet flow path from outlet 270 b is within 20 degrees of vertical. It may be noted that in this embodiment, outlet 270 b may be located on a different face than inlet 250 b. Further, outlet 270 a may be orthogonal to nearby inlet 250 b.

FIG. 3 illustrates another embodiment of a segmented heat sink 300. Segmented heat sink 300 may include a plurality of heat sink segments 320. Heat sink segments 320 may be adjacent a heat source 54. In various embodiments, heat source 54 may also be segmented into a plurality of heat sources 54 a-c. Segments of heat source 54 may correspond to electronic components. As shown in FIG. 3, each heat sink segment 320 may be positioned at an angle from a vertical line. An angle may allow individual heat sink segments 320 to be longer. Individual heat sink segments 320 may overlap. The angle may also allow beneficial positioning of inlets 350 and outlets 370. An angle may reduce the buoyant effect of warmed air and reduce air flow through a heat sink segment.

A middle heat sink segment 320 b may illustrate characteristics of this embodiment. Heat sink segment 320 b may include similar components to a heat sink segment 120. Base 330 b may be in thermal contact with heat source 54 b. Cover 340 b may cover the entire front surface of heat sink segment 320 b. In particular, cover 340 b may separate inlet 350 b from outlet 370 a. Cover 340 b may leave the bottom end of heat sink segment 320 b exposed for inlet 350 b. Inlet 350 b may be located on the bottom end face of heat sink segment 320 b and draw air vertically into heat sink segment 330 b. Inlet 350 b may be located substantially below outlet 370 a to prevent warm air from outlet 370 a from entering inlet 350 b. Inlet 350 b may be located such that at least fifty percent of inlet 350 b is below outlet 370 a. Vertical fins (not shown) may be located inside cover 240 b. The vertical fins may extend outward from base 330 b and dissipate heat as air rises within heat sink segment 320 b. Outlet 370 b may be located at the lateral faces of heat sink segment 320 b. Pins 360 b may extend outward from base 330 b and dissipate heat in the portion near outlet 370 b. Outlet 370 b may exhaust warm air substantially horizontally. The outlet flow path at outlet 370 b may be within 10 degrees of horizontal. It may be noted that in this embodiment, outlet 370 b may be located on a different face than inlet 350 b. Further, outlet 370 a may be orthogonal to nearby inlet 350 b.

FIG. 4 illustrates another embodiment of a segmented heat sink. This embodiment may include a cover 440 including one or more vertical baffles 445. The cover 440 may extend across a plurality of heat sink segments. As shown in FIG. 4, two heat sink segments 420 a and 420 b may be divided by a horizontal wall 455. Horizontal wall 455 may prevent fluid from flowing from heat sink segment 420 a to heat sink segment 420 b. In the bottom heat sink segment 420 a, an outlet 470 may be formed in cover 440. In this embodiment, the outlet 470 y be centrally located between two vertical baffles 445. The portion of heat sink segment 420 a below the outlet 470 may include vertical fins 465. Vertical fins 465 may extend vertically beneath cover 440 toward an inlet 450. The portion of the heat sink segment 420 a near outlet 470 may include pins 460, which may be spaced apart horizontally across the upper portion of heat sink segment 420 a. The pins 460 may allow air to flow horizontally toward the central outlet 470. Air exiting outlet 470 may be confined between the vertical baffles 445.

On the other side of horizontal wall 455, heat sink segment 420 b may include inlet 450. Cover 440 may define openings on the side and/or front of heat sink segment 420 b. The openings may be separated from outlet 470 by vertical baffles 445. The portion of heat sink segment 420 b near inlet 450 may include pins 460. Pins 460 may be spaced apart horizontally to allow air to flow horizontally inward and vertically upward. The portion of heat sink segment 420 b above the inlet 450 may include vertical fins 465. Vertical fins 465 may extend vertically beneath cover 440 toward the next outlet 470. The embodiment shown in FIG. 4 includes only two heat sink segments. Other embodiments may include additional heat sink segments. Cover 445 may be extended and define additional inlets 450 and outlets 470.

FIG. 5 illustrates another embodiment of a heat sink segment 520. Heat sink segment 520 may include base plate 530, cover 540, inlet 550, vertical fins 565, outlet 570, horizontal wall 575, and curved fins 580. Heat sink segment 520 may be placed in a placement position among other heat sink segments to form a heat sink. Heat sink segment 520 may be oriented as shown with curved fins 580 located near the top end of the heat sink segment 520 or oriented upside down such that the curved fins 580 are located near the bottom end. Other types of fins besides curved fins, such as angled straight fins, may also be used to allow air flow in the desired direction while also providing heat dissipation.

Curved fins 580 may extend from an opening such as outlet 570 to vertical fins 565. Curved fins 580 may be integrally formed with vertical fins 565. Alternatively, curved fins 580 may be attached to vertical fins 565 using welding or soldering. As with vertical fins 565, curved fins 580 may extend from base 530 toward a front face of heat sink segment 520. Curved fins 580 may dissipate heat from base 530. Curved fins 580 may direct a flow path of a fluid within heat sink segment 520. For example, curved fins 580 may direct air from the interior vertical fins 565 toward outlet 570 located on a side face of heat sink segment 520. Curved fins may direct a flow path so that an inlet flow path is approximately perpendicular to an outlet flow path. The approximately perpendicular flow paths may vary by up to 10 degrees.

FIG. 6 illustrates another embodiment of a heat sink segment 620. Heat sink segment 620 may include base plate 630, cover 640, inlet 650, vertical fins 665, outlet 670 and horizontal wall 675. Heat sink segment 620 may be placed in a placement position among other heat sink segments to form a heat sink. Heat sink segment 620 may be constructed such that the inlet 650 is located on a face on the back of the heat sink segment 620, and the outlet 670 is located on a face on the front of the heat sink segment 620. This arrangement may be advantageous as it allows the fins 665 to extend into the inlet and outlet regions, i.e., pins are not required, which can reduce fin surface area, and may also minimize the potential for mixing of outlet air with inlet air. In various embodiments, the inlet 650 may be located on a face on the front of the heat sink segment 620 and the outlet 670 may be located on the back of the heat sink segment 620. Also shown in FIG. 6, the side face of the heat sink segment 620 may be formed by a vertical fin 670. In this embodiment, cover plate 640 may form only the front face of heat sink segment 620.

FIG. 7 illustrates another embodiment of a heat sink 100 including ducts 190. Heat sink 700 may be similar to the heat sink 100 shown in FIGS. 1A-1C with like numerals indicating like parts. Heat sink 700 may further include ducts or plenum 190. In various embodiments, a heat sink segment may include inlet and outlet plenums, or ducts, which may be cylindrical, rectangular, square, etc., in shape. The plenum or ducts may be constructed of the same material as cover 140 and be formed integrally with cover 140. Alternatively, the plenum of ducts may be formed of a material with a high thermal conductivity to assist in heat dissipation. The plenums or ducts may be used to bring inlet air into the heat sink segments and exhaust outlet air away from the heat sink segments. The use of ducts may better ensure that outlet air does not mix with inlet air by making the locations of the air inlets and air outlets physically isolated. In the example embodiment shown in FIG. 7, ducts 190 may extend outward from heat sink segment 120 n and have an inlet 150 n located on the back face of heat sink 700. The inlet 150 n may face the opposite direction from outlet 170 a. The inlet flow path of inlet 150 n may be in the opposite direction of the outlet flow path of outlet 170 a. It should be apparent that plenum or ducts may be arranged in various configurations to provide inlets and outlets in appropriate locations with appropriate flow paths.

According to the foregoing, various exemplary embodiments provide for a segmented heat sink. In particular, by isolating an outlet air flow from an inlet air flow, the segmented heat sink may reduce reentrance of heated air.

Although the various exemplary embodiments have been described in detail with particular reference to certain exemplary aspects thereof, it should be understood that the invention is capable of other embodiments and its details are capable of modifications in various obvious respects. As is readily apparent to those skilled in the art, variations and modifications can be affected while remaining within the spirit and scope of the invention. Accordingly, the foregoing disclosure, description, and figures are for illustrative purposes only and do not in any way limit the invention, which is defined only by the claims. 

What is claimed is:
 1. A heat sink system comprising: a first heat sink segment, the first heat sink segment comprising a first heat sink base, a first fluid inlet, and a first fluid outlet having an outlet flow path, the first heat sink segment being positioned in a first placement position within the heat sink system; and a second heat sink segment, the second heat sink segment comprising a second heat sink base, a second fluid inlet having an inlet flow path, and a second fluid outlet, the second heat sink segment being positioned in a second placement position within the heat sink system based on the first placement position; wherein the second placement position is arranged so that the second fluid inlet receives fluid from substantially other sources than the first outlet flow path.
 2. The heat sink system of claim 1, wherein the second placement position is arranged vertically above and adjacent to the first placement position.
 3. The heat sink system of claim 1, wherein the first fluid outlet is located on a first face of the heat sink system and the second fluid inlet is located on a second face of the heat sink system.
 4. The heat sink system of claim 3, wherein the outlet flow path is approximately perpendicular to the inlet flow path.
 5. The heat sink system of claim 1, further comprising a cover plate comprising a first opening that at least partially defines the first fluid inlet and a second opening that at least partially defines the first fluid outlet.
 6. The heat sink of claim 5, wherein the cover plate comprises a vertical baffle located between the first fluid outlet and the second fluid inlet.
 7. The heat sink segment of claim 1, wherein the first fluid outlet comprises a plurality of pins projecting outwardly from the first heat sink base.
 8. The heat sink system of claim 1, wherein the second fluid inlet comprises a plurality of pins projecting outwardly from the second heat sink base.
 9. The heat sink system of claim 1, further comprising a horizontal wall separating the first heat sink segment and the second heat sink segment.
 10. The heat sink system of claim 1, wherein the first placement position overlaps the second placement position and at least one of the first heat sink segment and the second heat sink segment is oriented at an angle.
 11. The heat sink system of claim 10, wherein the first fluid outlet is above the second fluid inlet.
 12. The heat sink system of claim 10, wherein one of the first fluid inlet and the first fluid outlet is located at an end face of the first heat sink segment.
 13. A heat sink comprising: a base plate; a first heat sink segment comprising: a first plurality of vertical fins extending outwardly from the base plate toward a front face, a first fluid inlet, and a first fluid outlet; a second heat sink segment comprising: a second plurality of vertical fins extending outwardly from the base plate toward a front face, a second fluid inlet, and a second fluid outlet, the second heat sink segment located vertically above the first placement position; and a cover at least partially enclosing the first plurality of vertical fins and the second plurality of vertical fins and defining the first fluid outlet and the second fluid inlet.
 14. The heat sink of claim 13, wherein one of the first fluid outlet and the second fluid inlet is located on a front face of the heat sink system, and the other of the first fluid outlet and the second fluid inlet is located on a side face of the heat sink system.
 15. The heat sink of claim 13, further comprising a plurality of pins extending outwardly from the base plate toward the front face.
 16. The heat sink of claim 13, further comprising a horizontal wall separating the first heat sink segment and the second heat sink segment.
 17. The heat sink of claim 13, wherein the cover comprises a vertical baffle between the first fluid outlet and the second fluid inlet.
 18. The heat sink of claim 13 further comprising a duct adjacent one of the first fluid outlet and the second fluid inlet.
 19. A heat sink segment comprising: a base plate; a plurality of vertical fins, each fin extending outward from the base plate toward an edge located at a front face of the heat sink segment; a horizontal wall extending outward from the base plate at a first end of the plurality of vertical fins; a first fluid opening located at the first end of the heat sink segment; and a second fluid opening located at a second end of the heat sink segment, wherein the first fluid opening faces a different direction than the second fluid opening.
 20. The heat sink segment of claim 19, further comprising: a cover panel at least partially enclosing the plurality of vertical fins and defining the first fluid opening and the second fluid opening.
 21. The heat sink segment of claim 20, further comprising a plurality of spaced apart pins extending from the base plate toward the cover panel, wherein the cover panel defines openings on two side faces of the heat sink segment.
 22. The heat sink segment of claim 20, wherein the first fluid opening comprises a gap in the cover that exposes a portion of the vertical fins along the edges of the fins.
 23. The heat sink segment of claim 20, further comprising a plurality of curved fins extending from the base plate toward the cover panel, the curved fins extending from one of the first fluid opening and the second fluid opening toward the plurality of vertical fins.
 24. The heat sink segment of claim 19, wherein the first fluid opening is located on the front face of the of the heat sink segment and the second fluid opening is located on a face opposite the front face.
 25. The heat sink segment of claim 19 further comprising a duct or plenum. 